Modifications in number and morphology of dendritic spines resulting from chronic ethanol consumption and withdrawal: a Golgi study in the mouse anterior and posterior hippocampus

Substance use and spine density: a systematic review and meta-analysis of preclinical studies

The elucidation of synaptic density changes provides valuable insights into the underlying brain mechanisms of substance use. In preclinical studies, synaptic density markers, like spine density, are altered by substances of abuse (e.g., alcohol, amphetamine, cannabis, cocaine, opioids, nicotine). These changes could be linked to phenomena including behavioral sensitization and drug self-administration in rodents. However, studies have produced heterogeneous results for spine density across substances and brain regions. Identifying patterns will inform translational studies given tools that now exist to measure in vivo synaptic density in humans. We performed a meta-analysis of preclinical studies to identify consistent findings across studies. PubMed, ScienceDirect, Scopus, and EBSCO were searched between September 2022 and September 2023, based on a protocol (PROSPERO: CRD42022354006). We screened 6083 publications and included 70 for meta-analysis. The meta-analysis revealed drug-specific patterns in spine density changes. Hippocampal spine density increased after amphetamine. Amphetamine, cocaine, and nicotine increased spine density in the nucleus accumbens. Alcohol and amphetamine increased, and cannabis reduced, spine density in the prefrontal cortex. There was no convergence of findings for morphine's effects. The effects of cocaine on the prefrontal cortex presented contrasting results compared to human studies, warranting further investigation. Publication bias was small for alcohol or morphine and substantial for the other substances. Heterogeneity was moderate-to-high across all substances. Nonetheless, these findings inform current translational efforts examining spine density in humans with substance use disorders.

Behavioral changes and dendritic remodeling of hippocampal neurons in adolescent alcohol-treated rats

Objective: Earlier, we and others have reported that alcohol exposure in adolescent rat impaired performance of a spatial memory task in the Morris water maze. The goal of the present study was to investigate the effects of acute adolescent alcohol treatment on the hippocampus-dependent (contextual fear conditioning) and hippocampus-independent (cued fear) memories. The study also looked at the structural changes in anterior CA1 hippocampal neurons in adolescent alcohol-treated rats. Methods: Adolescent female rats were administered with a single dose of alcohol (1.0, 1.5, or 2.0 g/kg) or vehicle either before training (pre-training) or after training (pre-testing). Experimental and control rats were trained in the fear conditioning paradigm, and 24 h later tested for both contextual fear conditioning as well as cued fear memory. Separate groups of rats were treated with either alcohol (2 g/kg) or vehicle and sacrificed 24 h later. Their brains were harvested and processed for rapid Golgi staining. Randomly selected CA1 pyramidal neurons were analyzed for dendritic branching and dendritic spine density. Results: Pre-training alcohol dose-dependently attenuated acquisition of hippocampus-dependent contextual fear conditioning but had no effect on the acquisition of amygdala-associated cued fear. When administered following training (pre-testing), alcohol did not alter either contextual conditioning or cued fear memory. Golgi stained CA1 pyramidal neurons in alcohol treated female rats had reduced basilar tree branching and less complex dendritic arborization. Conclusion: Alcohol specifically impaired hippocampal learning in adolescent rats but not amygdala-associated cued fear memory. Compared to vehicle-treated rats, CA1 hippocampal pyramidal neurons in alcohol-treated rats had less complex dendritic morphology. Together, these data suggest that adolescent alcohol exposure produces changes in the neuronal organization of the hippocampus, and these changes may be related to impairments in hippocampus-dependent memory formation.

Biological intersection of sex, age, and environment in the corticotropin releasing factor (CRF) system and alcohol

The neuropeptide corticotropin-releasing factor (CRF) is critical in neural circuit function and behavior, particularly in the context of stress, anxiety, and addiction. Despite a wealth of preclinical evidence for the efficacy of CRF receptor 1 antagonists in reducing behavioral pathology associated with alcohol exposure, several clinical trials have had disappointing outcomes, possibly due to an underappreciation of the role of biological variables. Although he National Institutes of Health (NIH) now mandate the inclusion of sex as a biological variable in all clinical and preclinical research, the current state of knowledge in this area is based almost entirely on evidence from male subjects. Additionally, the influence of biological variables other than sex has received even less attention in the context of neuropeptide signaling. Age (particularly adolescent development) and housing conditions have been shown to affect CRF signaling and voluntary alcohol intake, and the interaction between these biological variables is particularly relevant to the role of the CRF system in the vulnerability or resilience to the development of alcohol use disorder (AUD). Going forward, it will be important to include careful consideration of biological variables in experimental design, reporting, and interpretation. As new research uncovers conditions in which sex, age, and environment play major roles in physiological and/or pathological processes, our understanding of the complex interaction between relevant biological variables and critical signaling pathways like the CRF system in the cellular and behavioral consequences of alcohol exposure will continue to expand ultimately improving the ability of preclinical research to translate to the clinic. This article is part of the special issue on Neuropeptides.

Effect of Alcohol on Hippocampal-Dependent Plasticity and Behavior: Role of Glutamatergic Synaptic Transmission

Problematic alcohol drinking and alcohol dependence are an increasing health problem worldwide. Alcohol abuse is responsible for approximately 5% of the total deaths in the world, but addictive consumption of it has a substantial impact on neurological and memory disabilities throughout the population. One of the better-studied brain areas involved in cognitive functions is the hippocampus, which is also an essential brain region targeted by ethanol. Accumulated evidence in several rodent models has shown that ethanol treatment produces cognitive impairment in hippocampal-dependent tasks. These adverse effects may be related to the fact that ethanol impairs the cellular and synaptic plasticity mechanisms, including adverse changes in neuronal morphology, spine architecture, neuronal communication, and finally an increase in neuronal death. There is evidence that the damage that occurs in the different brain structures is varied according to the stage of development during which the subjects are exposed to ethanol, and even much earlier exposure to it would cause damage in the adult stage. Studies on the cellular and cognitive deficiencies produced by alcohol in the brain are needed in order to search for new strategies to reduce alcohol neuronal toxicity and to understand its consequences on memory and cognitive performance with emphasis on the crucial stages of development, including prenatal events to adulthood.

New insights on neurobiological mechanisms underlying alcohol addiction

Alcohol dependence/addiction is mediated by complex neural mechanisms that involve multiple brain circuits and neuroadaptive changes in a variety of neurotransmitter and neuropeptide systems. Although recent studies have provided substantial information on the neurobiological mechanisms that drive alcohol drinking behavior, significant challenges remain in understanding how alcohol-induced neuroadaptations occur and how different neurocircuits and pathways cross-talk. This review article highlights recent progress in understanding neural mechanisms of alcohol addiction from the perspectives of the development and maintenance of alcohol dependence. It provides insights on cross talks of different mechanisms and reviews the latest studies on metaplasticity, structural plasticity, interface of reward and stress pathways, and cross-talk of different neural signaling systems involved in binge-like drinking and alcohol dependence.

Neurochemical and neurostructural plasticity in alcoholism

The behavioral manifestations of alcoholism are primarily attributable to the numerous and lasting adaptations that occur in the brain as a result of chronic heavy alcohol consumption. As will be reviewed here, these adaptations include alcohol-induced plasticity in chemical neurotransmission, density and morphology of dendritic spines, as well as neurodegeneration and cerebral atrophy. Within the context of these neuroadaptations that have been observed in both human and animal studies, we will discuss how these changes potentially contribute to the cognitive and behavioral dysfunctions that are hallmark features of alcoholism, as well as how they reveal novel potential pharmacological targets for the treatment of this disorder.

The role of amygdaloid brain-derived neurotrophic factor, activity-regulated cytoskeleton-associated protein and dendritic spines in anxiety and alcoholism

Innate anxiety appears to be a robust factor in the promotion of alcohol intake, possibly due to the anxiolytic effects of self-medication with alcohol. Brain-derived neurotrophic factor (BDNF) and its downstream target, activity-regulated cytoskeleton-associated (Arc) protein, play a role in the regulation of synaptic function and structure. In order to examine the role of the BDNF-Arc system and associated dendritic spines in the anxiolytic effects of ethanol, we investigated the effects of acute ethanol exposure on anxiety-like behaviors of alcohol-preferring (P) and -nonpreferring (NP) rats. We also examined changes in the expression of BDNF and Arc, and dendritic spine density (DSD), in amygdaloid brain regions of P and NP rats with or without ethanol exposure. It was found that in comparison with NP rats, P rats displayed innate anxiety-like behaviors, and had lower mRNA and protein levels of both BDNF and Arc, and also had lower DSD in the central amygdala (CeA) and medial amygdala (MeA), but not in the basolateral amygdala (BLA). Acute ethanol treatment had an anxiolytic effect in P, but not in NP rats, and was associated with an increase in mRNA and protein levels of BDNF and Arc, and in DSD in the CeA and MeA, but not BLA. These results suggest that innate deficits in BDNF-Arc levels, and DSD, in the CeA and MeA may be involved in the anxiety-like and excessive alcohol-drinking behaviors of P rats, as ethanol increased these amygdaloid synaptic markers and produced anxiolytic effects in P rats, but not NP rats.

Neuroscience of alcoholism: molecular and cellular mechanisms

Alcohol use and abuse appear to be related to neuroadaptive changes at functional, neurochemical, and structural levels. Acute and chronic ethanol exposure have been shown to modulate function of the activity-dependent gene transcription factor, cAMP-responsive element binding (CREB) protein in the brain, which may be associated with the development of alcoholism. Study of the downstream effectors of CREB have identified several important CREB-related genes, such as neuropeptide Y, brain-derived neurotrophic factor, activity-regulated cytoskeleton-associated protein, and corticotrophin-releasing factor, that may play a crucial role in the behavioral effects of ethanol and molecular changes in the specific neurocircuitry that underlie both alcohol addiction and a genetic predisposition to alcoholism. Brain chromatin remodeling due to histone covalent modifications may also be involved in mediating the behavioral effects and neuroadaptive changes that occur during ethanol exposure. This review outlines progressive neuroscience research into molecular and epigenetic mechanisms of alcoholism.

Chronic cigarette smoking modulates injury and short-term recovery of the medial temporal lobe in alcoholics

Memory function is largely mediated by the medial temporal lobe (MTL), and its compromise has been observed in alcohol dependence and chronic cigarette smoking. The effects of heavy alcohol consumption and chronic smoking on hippocampal volumes and MTL metabolites and their recovery during abstinence from alcohol have not been assessed. Male alcoholics in treatment (ALC) [13 smokers (sALC) and 11 non-smokers (nsALC)] underwent quantitative magnetic resonance imaging and short-echo proton magnetic resonance spectroscopic imaging at 1 week and 1 month of sobriety. Outcome measures were compared with 14 age-matched, non-smoking light-drinkers and were related to visuospatial learning and memory. Over 1 month of abstinence, N-acetyl-aspartate, a neuronal marker, and membrane-associated choline-containing metabolites normalized in the MTL of nsALC subjects, but remained low in the MTL of sALC subjects. Metabolite concentration changes in both groups were associated with improvements in visuospatial memory. Hippocampal volumes increased in both groups during abstinence, but increasing volumes correlated with visuospatial memory improvements only in nsALC subjects. In summary, chronic cigarette smoking in alcohol-dependent men appears to have adverse effects on MTL metabolite recovery during short-term sobriety. These data may also have implications for other conditions with established MTL involvement and significant smoking co-morbidity, such as schizophrenia-spectrum and mood disorders.

Homers regulate drug-induced neuroplasticity: implications for addiction

Drug addiction is a chronic, relapsing disorder, characterized by an uncontrollable motivation to seek and use drugs. Converging clinical and preclinical observations implicate pathologies within the corticolimbic glutamate system in the genetic predisposition to, and the development of, an addicted phenotype. Such observations pose cellular factors regulating glutamate transmission as likely molecular candidates in the etiology of addiction. Members of the Homer family of proteins regulate signal transduction through, and the trafficking of, glutamate receptors, as well as maintain and regulate extracellular glutamate levels in corticolimbic brain regions. This review summarizes the existing data implicating the Homer family of protein in acute behavioral and neurochemical sensitivity to drugs of abuse, the development of drug-induced neuroplasticity, as well as other behavioral and cognitive pathologies associated with an addicted state.

Red wine antioxidants protect hippocampal neurons against ethanol-induced damage: A biochemical, morphological and behavioral study

Chronic ethanol consumption increases oxidative stress, which accounts for the striking neurological changes seen in this condition. Notwithstanding, there is well-documented evidence that polyphenols, present in grape skin and seeds, exhibit a strong antioxidant activity. As red wine is rich in polyphenols, the aim of the present work was to evaluate their putative protective effects on the hippocampal formation by applying biochemical, morphological and behavioral approaches. Six-month old male Wistar rats were fed with red wine (ethanol content adjusted to 20%) and the results were compared with those from ethanol-treated (20%) rats and pair-fed controls. Biochemical markers of oxidative stress (lipid peroxidation, glutathione levels and antioxidant enzyme activities) were assessed on hippocampal homogenates. Lipofuscin pigment, an end product of lipid peroxidation, was quantified in hippocampal cornu ammonis 1 and 3 (CA1 and CA3) pyramidal neurons using stereological methods. All animals were behaviorally tested on the Morris water maze in order to assess their spatial learning and memory skills. In red wine-treated rats, lipid peroxidation was the lowest while presenting the highest levels of reduced glutathione and an induction of antioxidant enzyme activities. Morphological findings revealed that, contrary to ethanol, red wine did not increase lipofuscin deposition in CA1 and CA3 pyramidal neurons. Besides, red wine-treated animals learned the water maze task at a higher rate than ethanol group and had better performance scores by the end of the training period and on a probe trial. Actually, no significant differences were found between pair-fed controls and red wine-treated rats in morphological and behavioral data. Thus, our findings demonstrate that chronic consumption of red wine, unlike the ethanol solution alone, does not lead to a decline in hippocampal-dependent spatial memory. This may be due to the ability of red wine polyphenols to improve the antioxidant status in the brain and to prevent free radical-induced neuronal damage.

Adaptive plasticity of NMDA receptors and dendritic spines: implications for enhanced vulnerability of the adolescent brain to alcohol addiction

It is now known that brain development continues into adolescence and early adulthood and is highly influenced by experience-dependent adaptive plasticity during this time. Behaviorally, this period is also characterized by increased novelty seeking and risk-taking. This heightened plasticity appears to be important in shaping behaviors and cognitive processes that contribute to proper development of an adult phenotype. However, increasing evidence has linked these same experience-dependent learning mechanisms with processes that underlie drug addiction. As such, the adolescent brain appears to be particularly susceptible to experience-dependent learning processes associated with consumption of alcohol and addictive drugs. At the level of the synapse, homeostatic changes during ethanol consumption are invoked to counter the destabilizing effects of ethanol on neural networks. This homeostatic response may be especially pronounced in the adolescent and young adult brain due to its heightened capacity to undergo experience-dependent changes, and appears to involve increased synaptic targeting of NMDA receptors. Interestingly, recent work from our lab also indicates that the enhanced synaptic localization of NMDA receptors promotes increases in the size of dendritic spines. This increase may represent a structural-based mechanism that supports the formation and stabilization of maladapted synaptic connections that, in a sense, "fix" the addictive behavior in the adolescent and young adult brain.

Adult neurogenesis: from precursors to network and physiology

The discovery that the adult mammalian brain creates new neurons from pools of stemlike cells was a breakthrough in neuroscience. Interestingly, this particular new form of structural brain plasticity seems specific to discrete brain regions, and most investigations concern the subventricular zone (SVZ) and the dentate gyrus (DG) of the hippocampal formation (HF). Overall, two main lines of research have emerged over the last two decades: the first aims to understand the fundamental biological properties of neural stemlike cells (and their progeny) and the integration of the newly born neurons into preexisting networks, while the second focuses on understanding its relevance in brain functioning, which has been more extensively approached in the DG. Here, we propose an overview of the current knowledge on adult neurogenesis and its functional relevance for the adult brain. We first present an analysis of the methodological issues that have hampered progress in this field and describe the main neurogenic sites with their specificities. We will see that despite considerable progress, the levels of anatomic and functional integration of the newly born neurons within the host circuitry have yet to be elucidated. Then the intracellular mechanisms controlling neuronal fate are presented briefly, along with the extrinsic factors that regulate adult neurogenesis. We will see that a growing list of epigenetic factors that display a specificity of action depending on the neurogenic site under consideration has been identified. Finally, we review the progress accomplished in implicating neurogenesis in hippocampal functioning under physiological conditions and in the development of hippocampal-related pathologies such as epilepsy, mood disorders, and addiction. This constitutes a necessary step in promoting the development of therapeutic strategies.

Nigrostriatal modifications after vanadium inhalation: an immunocytochemical and cytological approach

Vanadium (V) has increased in the air as a component of suspended particles originated from fuel combustion. In this report, a model of inhaled V in mice was implemented to identify the effect that V has in the corpus striatum and substantia nigra, structures with high concentrations of dopamine and scarce antioxidants burden. Mice inhaled 0.02 M V2O5 1 h twice a week and were sacrificed at points from 1 to 8 weeks after inhalation, perfused, and processed for Golgi method and for tyroxine hidroxylase (TH) inmunocytochemistry. Cytological analysis consisted in counting the number of dendritic spines in 20 medium-size spiny neurons and the number of TH immunoreactive neurons in the substatia nigra pars compacta. Dendritic spine density decreased drastically after V exposure; the same was observed with the TH-positive neurons, which decreased in a time-dependent mode. No previous morphological studies about V and nervous system have been reported. The decrease in spine density and in TH-positive neurons might have functional repercussions that should be studied because the trend of this element in the atmosphere is to increase.

Age-dependent effects of moderate chronic ethanol administration on different forms of memory expression in mice

A large number of studies have investigated the effects of chronic ethanol administration (CEA) on performance in different types of learning and memory tasks in adult rodents. As a general rule, CEA has been reported to impair performance, although this depends both on the condition of administration (e.g. duration, presence or not of a withdrawn period) and on task demands (e.g. spatial versus non-spatial). Indeed, either no impairment or even a facilitation of performance have been reported following CEA. However, no study has directly addressed the issue as to whether the effect of CEA depends on the age of subjects. In this study, C57Bl/6 mice of two age ranges (i.e. 2-3- and 16-18-month-old) were given either a solution of ethanol (12% v/v) as their only source of fluid for 5 months (experimental groups) or were pair-fed with an isocaloric solution of dextri-maltose (control groups). Then, they were submitted to a place discrimination task in an 8-arm radial maze. Additionally, mice were tested for long-term retention following a 21-day interval. Confirming our previous findings, the results showed that, with respect to adults (7-8-month-old at the time of testing), aged mice (21-23-month-old) of the control group displayed impaired relational memory but not procedural memory performance. Further they exhibited a higher level of forgetting than adults over the 21-day interval. In the same paradigm, CEA resulted in an overall attenuation of both type of deficit in aged subjects without altering their procedural memory. Furthermore these ethanol-consuming aged mice displayed significantly less levels of forgetting than their age-matched controls. Conversely, in the adult group, CEA resulted in an overall, although, somewhat less selective impairment of relational memory with respect to procedural memory but had no effect on long-term forgetting. While confirming the deleterious effect of CEA on learning and memory processes in adults, our present findings provide evidence that CEA can selectively ameliorate certain cognitive deficits normally associated with ageing.

Differential effects of learning on neurogenesis: learning increases or decreases the number of newly born cells depending on their birth date

The hippocampal formation, to which new neurons are added on a daily basis throughout life, is important in spatial learning. Surviving de novo produced cells integrate into the functional circuitry, where they can influence both normal and pathological behaviors. In this study, we examined the effect of the water-maze (a hippocampal-dependent spatial task) on neurogenesis. Learning in this task can be divided into two phases, an early phase during which performance improves rapidly, and a late phase during which asymptotic levels of performance are reached. Here we demonstrate that the late phase of learning has a multifaceted effect on neurogenesis depending on the birth date of new neurons. The number of newly born cells increased contingently with the late phase and a large proportion of these cells survived for at least 4 weeks and differentiated into neurons. In contrast, late-phase learning decreased the number of newly born cells produced during the early phase. This decline in neurogenesis was positively correlated with performance in the water-maze. Thus, rats with the highest de novo cell number were less able to acquire and use spatial information than those with low numbers of new cells. These results show that learning has a complex effect on hippocampal neurogenesis, and reveals a novel mechanism through which neurogenesis may influence normal and pathological behaviors.

Ethanol and brain plasticity: receptors and molecular networks of the postsynaptic density as targets of ethanol

Brain plasticity refers to the ability of the brain to undergo structural and functional changes. It is a necessary process that allows us to adapt and learn from our environment and is fundamental to our survival. However, under certain conditions, these neuroadaptive responses can have adverse consequences. In particular, increasing evidence indicates that plastic processes are coopted by drugs of abuse, leading to addiction and associated drug-seeking behaviors. An extensive and diverse group of studies ranging from the molecular to the behavioral level has also strongly implicated glutamatergic neurotransmission as a critical mediator of experience-dependent synaptic plasticity. Thus, it is vital to understand how drugs of abuse interact and potentially alter glutamatergic neurotransmission and associated signal transduction processes. This review will focus on the cellular and molecular neuroscience of alcoholism, with emphasis on events at the glutamatergic postsynaptic density (PSD) and dendritic spine dynamics that appear to underlie much of the structural and functional plasticity of the CNS.

Chronic ethanol consumption restores the age-related decrease in neurogranin mRNA level in the hippocampus of mice

Neurogranin (Ng) is a Ca(2+)-sensitive calmodulin-binding neuron-specific protein that has been implicated in the regulation of numerous post-synaptic signalling pathways. Here, we investigate the effects of 5 months low level ethanol consumption (approximately 20% of total calories intake) on Ng mRNA expression in the brain of adult (approximately 7-8 months) and aged (approximately 21-22 months) mice using in situ hybridization histochemistry. Results showed that ageing was accompanied by a decrease in amounts of mRNA coding for Ng, especially in the hippocampus (approximately 25% of adults) known to play a critical role in higher cognitive functions. Chronic ethanol consumption restored this decline up to pre-senescent (adult) levels without altering Ng mRNA levels in adult mice. On the basis of recent data indicating a central role for Ng in the regulation of hippocampal synaptic plasticity and spatial learning, our results suggest that moderate ethanol consumption might have a beneficial influence on cognitive deterioration during senescence. Such a possibility is in fact congruent with recent follow-up studies conducted in elderly people.

Dendritic spine pathology: cause or consequence of neurological disorders?

Altered dendritic spines are characteristic of traumatized or diseased brain. Two general categories of spine pathology can be distinguished: pathologies of distribution and pathologies of ultrastructure. Pathologies of spine distribution affect many spines along the dendrites of a neuron and include altered spine numbers, distorted spine shapes, and abnormal loci of spine origin on the neuron. Pathologies of spine ultrastructure involve distortion of subcellular organelles within dendritic spines. Spine distributions are altered on mature neurons following traumatic lesions, and in progressive neurodegeneration involving substantial neuronal loss such as in Alzheimer's disease and in Creutzfeldt-Jakob disease. Similarly, spine distributions are altered in the developing brain following malnutrition, alcohol or toxin exposure, infection, and in a large number of genetic disorders that result in mental retardation, such as Down's and fragile-X syndromes. An important question is whether altered dendritic spines are the intrinsic cause of the accompanying neurological disturbances. The data suggest that many categories of spine pathology may result not from intrinsic pathologies of the spiny neurons, but from a compensatory response of these neurons to the loss of excitatory input to dendritic spines. More detailed studies are needed to determine the cause of spine pathology in most disorders and relationship between spine pathology and cognitive deficits.

Motor impairments in an oxidative stress model and its correlation with cytological changes on rat striatum and prefrontal cortex

Exposure to ozone results in an increased production of free radicals which causes oxidative stress. The purpose of this study was to determine the effects of ozone exposure on motor behavior and its correlation with the cytology of the striatum and prefrontal cortex. Twenty-four male Wistar rats were exposed to 1 p.p.m. (parts per million) ozone for 4 hrs in a closed chamber. Control group was exposed to flowing air. Twenty-four hours after ozone exposure, the motor behavior was measured. After that, the animals were perfused and the brains were placed in Golgi stain. The analysis consisted in counting the dendritic spines in 5 secondary and 5 tertiary dendrites of each of the 20 medium size spiny neurons of striatum and 20 pyramidal neurons of prefrontal cortex analyzed. Our results showed alterations in motor behavior and a significant reduction of dendritic spines, and provided evidence that the deterioration in motor behavior is probably due to the reduction in spine density in the neurons of striatum and prefrontal cortex.

Decreased expression of MAP-2 and GAD in the brain of cats infected with feline immunodeficiency virus

HIV-1 infection is often complicated by the dysfunction of central nervous system (CNS). Degenerative neuronal changes as well as neuronal loss have been documented in individuals with acquired immunodeficiency syndrome. Feline immunodeficiency virus (FIV) causes similar CNS manifestation and FIV infected cats provide an animal model for human immunodeficiency virus infection in humans. In this study, we examined the brain of FIV-infected cats and controls with immunohistochemical techniques using antibodies to microtubule-associated protein 2 (MAP-2) and glutamic acid decarboxylase (GAD). We found a significant decrease in expression of MAP-2 and GAD in neurons of infected animals compared to controls. In contrast, the expression of neurofilaments and glial fibrillary acidic protein was rather increased. The changes observed in the brain were similar to those seen in humans undergoing the normal aging process as well as those suffering from neurological diseases like Alzheimer's disease and other dementing disorders. These changes in the feline brain give insight into the deleterious effects of FIV on the CNS.

Prenatal and postnatal exposure to ethanol induces changes in the shape of the dendritic spines from hippocampal CA1 pyramidal neurons of the rat

20%-ethanol was provided to adult female rats since a pregestational stage until weaning of the pups, and percentage proportion of thin, mushroom-shaped, stubby, or wide spines from the apical dendrite of hippocampal CA1 pyramidal cells, was counted at 15, 21, 40, and 90 days of age. By-kind-of-spine analysis revealed higher fluctuation of experimental spines, and less percentage of thin spines was observed in the ethanol-intoxicated rats concomitantly with a higher proportion of stubby or wide spines; through development. Because thin spines may propagate the synaptic potentials more efficiently than stubby or wide spines, this findings suggest that the electrical excitability and thereafter the firing pattern of those cells may be altered, due to the toxic effects of chronic ethanol ingestion.

Synaptic reorganization in the hippocampal formation of alcohol-fed rats may compensate for functional deficits related to neuronal loss

We have examined the behavioral and neuroanatomical effects of long-term alcohol intake in rats ingesting a 20% solution of ethanol for 30 weeks. Previous studies have shown that this treatment provokes neuronal degeneration in the hippocampal formation, which occurs in parallel with remodeling processes. Spatial reference and working memory of alcohol-fed rats were evaluated during last 4 weeks of treatment by comparison of their performance with age-matched controls on the Morris water maze. Alcohol consumption did not affect the performance of rats in the reference memory task as indicated by the measures derived from the acquisition trials and from the probe-trial, which were highly similar for alcohol-fed and control animals. Also, performance in the working memory task was not significantly altered in alcohol-treated animals. No treatment-related changes in swim speed or impairments of sensorimotor abilities, tested in the visible platform task, were detected. Stereological methods were applied to evaluate the damage inflicted by alcohol intake in the structure of the hippocampal formation. In the alcohol-treated animals, there was a noticeable cell loss in the granular layer of the dentate gyrus (10%), and in CA3 (18%) and CA1 (19%) hippocampal subdivisions. In spite of the neuronal loss, the total number of synapses between mossy fibers and CA3 pyramids was unaffected by alcohol treatment suggesting that new synaptic contacts were formed between the surviving neurons. We show that, regardless the marked hippocampal cell loss in rats exposed to chronic alcohol intake, the reorganization that takes place at the synaptic level may alleviate the expected functional deficits.

Memory deterioration in an oxidative stress model and its correlation with cytological changes on rat hippocampus CA1

Exposure to ozone results in an increased production of free radicals which causes oxidative stress. The purpose of this study was to determine the effects of ozone exposure on memory and its correlation with the cytology of the hippocampus. Twenty-four male Wistar rats were exposed to 1 ppm (parts per million) ozone for 4 h in a closed chamber. Control group was exposed to flowing air. After ozone exposure, the rats were given long-term (24 h) memory training which consists of a passive avoidance conditioning. After that the animals were perfused and the brains were placed in the Golgi stain. The analysis consisted in counting the dendritic spines in five secondary and five tertiary dendrites of each of the 20 pyramidal neurons of hippocampus CA1 analyzed. Our results showed alterations on long-term memory and a significant reduction of dendritic spines, and provided evidence that this deterioration in memory is probably due to the reduction in spine density in the pyramidal neurons of hippocampus.

Behavioral and neuroanatomical consequences of chronic ethanol intake and withdrawal

We have examined if long-term (13 months) alcohol consumption and the same treatment followed by a 6-week withdrawal period cause different neuropathological changes in rats. Spatial reference and working memory of alcohol-consuming and withdrawn rats were evaluated by comparison of their performance with age-matched controls in the Morris water maze. In the reference memory task we did not observe significant cognitive deficits in rats continuously exposed to ethanol, whereas withdrawn animals showed an obvious impairment of their overall performance. The reference memory deficit in withdrawn rats was evident in the spatial probe trial; these animals required significantly longer swimming distances to approach the former position of the platform when compared with controls and alcohol-consuming animals. In contrast, working memory was not significantly altered in either experimental group. Stereological methods were applied to compare the neurodegenerative changes produced by alcohol intake and withdrawal in the hippocampal formation. In the alcohol-consuming animals there was a significant cell loss in CA1 (18%) and CA3 (19%) hippocampal regions. Moreover, in withdrawn rats there was a further decay in the total number of pyramidal neurons, which amounted to 15% relative to nonwithdrawn animals. In the granular layer of the dentate gyrus there was a trend in the same direction, but it did not reach significance. Thus, our findings indicate that withdrawn rats are cognitively impaired relative to animals submitted to continuous alcohol consumption and to age-matched controls, which fits the morphological data showing that withdrawal aggravates ethanol-induced degenerative processes in the hippocampal formation.

Progressive dendritic pathology in cynomolgus macaques infected with simian immunodeficiency virus

Neuronal pathology in acquired immunodeficiency syndrome (AIDS) is of interest in relation to cognitive impairment in AIDS patients and from the broader perspective of the pathogenesis of neurodegeneration. Cortical dendritic spine loss has been described in patients with AIDS and the aim of this study was to test the hypothesis that similar pathology is present in cynomolgus macaques infected with simian immunodeficiency virus (SIV). These animals develop an AIDS-like illness, but multinucleated giant cell encephalitis is not a feature and CNS virus load is found to be very low. Four animals infected for 2.5-3 months and four infected for 2-3 years were compared with four controls. The Golgi-Cox technique was employed to demonstrate dendritic morphology in the frontal cortex and the diameter of apical dendrites, dendritic spine density and dendritic spine lengths were measured in layer V pyramidal cells. Immunohistochemistry for microtubule-associated protein-2 (MAP-2), MHC class II and glial fibrillary acidic protein (GFAP) was also performed. In infected animals there was progressive spine loss and atrophy of remaining spines with loss of MAP-2 immunoreactivity at late time points. No parallel increase in GFAP immunostaining or MHC-class II expression in microglial cells was seen. We conclude that progressive neuronal dendritic pathology is a feature of SIVmac251 infection of cynomolgus macaques and is apparent relatively early in disease. Furthermore, dendritic abnormalities occur in the absence of either multinucleated giant cell pathology or substantial CNS virus load.

Effects of alcohol on the synthesis and expression of hypothalamic peptides

Studies aimed at analyzing the deleterious effects of excess alcohol in the brain have revealed structural alterations that are often associated with functional and behavioral disturbances. Among the neuronal damage related to prolonged alcohol exposure, alterations in the synthesizing capabilities and levels of expression of neuroactive peptides have been increasingly reported. Actually, such changes frequently represent the sole repercussion of acute and short-term exposure to ethanol. This review gathers the existing data on the effects of ethanol exposure on the synthesis and expression of hypothalamic peptides. Amid those that can act both as neurotransmitters and neurohormones, we allude to vasopressin, corticotropin-releasing hormone, thyrotropin-releasing hormone and pro-opiomelanocortin and related peptides produced by paraventricular, supraoptic and arcuate neurons. With respect to peptides that act exclusively as neurotransmitters, we address the effects of alcohol on vasoactive intestinal polypeptide, gastrin-releasing peptide, somatostatin and vasopressin synthesized by suprachiasmatic neurons. Hypothalamic neurons that produce peptides that act as neurotransmitters are supposed to be modulated primarily by influences exerted by neuronal afferents, whereas those producing peptides that additionally act as neurohormones are also regulated by peripheral stimuli (e.g., plasma levels of circulating hormones, osmotic challenges). These peculiar features endue the hypothalamus with characteristics that are particularly propitious to enlighten the still cryptic mechanisms underlying the ethanol effects on protein synthesis.

Abstinent chronic crack-cocaine and crackcocaine/alcohol abusers evidence normal hippocampal volumes on MRI despite persistent cognitive impairments

We measured hippocampal volumes and cognitive functioning in crack-cocaine and crack-cocaine/alcoholdependent subjects (abstinent approximately 10-12 weeks) compared to age-matched controls. Cognitive function was evaluated using the computerized MicroCog Assessment of Cognitive Functioning (which includes tests of explicit, declarative memory subserved by the hippocampus). The hippocampal volumes were quantified on T1-weighted MRIs and were expressed as a proportion of intracranial vault volume. Both subjects and controls showed the larger right versus left hippocampal volume expected in normal anatomy, but we found no differences in hippocampal volume between any of the groups. However, both abstinent cocaine-dependent subjects and abstinent cocaine/alcohol-dependent subjects showed persistent cognitive impairments, including deficits in explicit memory. Our results suggest that either: (1) the hippocampus is resistant to structural volume loss in young and middle-aged cocaine or cocaine/alcohol-dependent subjects, (2) the hippocampal volume loss suffered by young and middle-aged cocaine or cocaine/alcohol-dependent subjects resolves after approximately 3 months of abstinence, or (3) hippocampal atrophy is obscured by the process of gliosis. Further, the cognitive impairments persisting in these abstinent cocaine and cocaine/alcohol-dependent samples may (1) be unrelated to hippocampal function or (2) be associated with abnormal hippocampal function that is not reflected in MRI measures of overall hippocampal atrophy.

The effects of single and repeated episodes of thiamin deficiency on memory in alcohol-consuming rats

The underlying pathogenesis of Korsakoff's syndrome, an amnesic disorder most commonly found in alcoholics, is not well understood. Chronic alcoholism is associated with thiamin deficiency and current thinking is that this may be the causal factor. In Experiment 1, rats were given a 20% (v/v) ethanol/water mix as their only source of fluid for 156 days. Three groups were made thiamin deficient through the combination of a thiamin-deficient diet and the centrally acting thiamin antagonist pyrithiamin hydrobromide, after 4, 15, and 26 weeks exposure to ethanol, respectively. The control group was given ad lib access to laboratory chow and water throughout this period. There were no differences between groups on either the working or reference versions of the Morris water tank paradigm. In Experiment 2, to test the hypothesis that a single bout of thiamin deficiency, with or without concurrent alcohol intake, is not sufficient to cause severe memory impairments, two groups of rats were subjected to three bouts of thiamin deficiency. One of these groups consumed an ethanol/water mix, the other tap water. A third group was made thiamin deficient on only one occasion. The control group was not made thiamin deficient and consumed lab chow and tap water throughout. Once again, there were no between-group differences in the data derived from testing in either the eight-arm radial maze or the Morris water tank task. These experiments indicate that the aetiology of Korsakoff's syndrome is more complex than previously thought.

Can megadoses of thiamine prevent ethanol-induced damages of rat hippocampal CA1 pyramidal neurones?

The specific aim of this study was to evaluate whether high doses of thiamine can compensate or prevent alcohol-induced damages of rat hippocampus CA1 pyramids. Twenty weeks of ethanol consumption together with a dose of thiamine in the range of 1.19 mg/100 mg food induced significant enlargement (parameters measured were length of the whole spine and diameter of the end-bulb) of dendritic spines. Hypertrophy can be interpreted as a compensation process due to alcohol-induced cell death because viable spines are in search of new synaptic contacts. In contrast, dendritic spines of the alcohol group fed at the same time with a high dose of thiamine (119 mg/ 100 g food = megavitamintherapy) showed normal data concerning these parameters. From these results it may be concluded that a megavitamin therapy supports a neuron's carbohydrate metabolism and therefore could be able to prevent or reduce alcohol-induced damages of hippocampal CA1 pyramidal cells in rat central nervous system.

Reduction of regional brain glucose metabolism following different durations of chronic ethanol consumption in mice: a selective effect on diencephalic structures

The effects of chronic alcohol consumption on regional brain glucose metabolism were examined in Balb/c mice using the [14C]2-deoxyglucose autoradiographic technique. Animals were given a solution of 12% v/v ethanol as their only source of fluid for either 6, 12 or 18 months and compared to control groups receiving either an isocaloric solution or saccharose or tap water. Alterations of cerebral brain glucose metabolism were assessed in mice who were returned to a non-alcoholic diet and allowed to freely explore a T-maze. The results showed that chronic ethanol consumption induced reductions of regional metabolic activity which were functions both of the duration of alcohol treatment and of the structure studied. Whereas a six month period of alcoholization did not induce any significant effects on metabolic activity, 12 months of treatment were necessary to induce the first observable and significant reductions in [14C]2-deoxyglucose labelling. These effects were mainly limited to diencephalic structures such as the lateral mammillary nuclei and the anterodorsal thalamic nuclei. The cerebellum was also affected but to a lesser degree. After 18 months of alcoholization, a generalized spread of the metabolic reduction to the entire mammillary complex (lateral, medial and posterior nuclei) and to the thalamic nuclei was observed. This same duration of treatment was necessary to induce the first detectable decrease of metabolic activity in the hippocampus. In agreement with data from human neuropathology, these findings confirm the particular vulnerability of diencephalic structures to ethanol and suggest that damage limited to diencephalic regions rather than to hippocampal or cortical areas could be primarily responsible for the memory disorders observed in Korsakoff's syndrome.

Changes in human plasma nerve growth factor level after chronic alcohol consumption and withdrawal

Numerous studies reported in recent years have shown that withdrawal from chronic consumption of drugs induces high levels of anxiety, both in humans and in animal models. In the present study, we demonstrated that withdrawal from chronic consumption of either ethanol or heroin causes a significant increase in plasma nerve growth factor, suggesting that the resulting anxiety condition triggers the release of this molecule. Although the functional significance of this phenomenon needs to be better defined, it is hypothesized that the increased levels of circulating nerve growth factor might be involved in homeostatic adaptive and/or reparative mechanisms.

Chronic ethanol consumption increases the amount of mRNA for retinoic acid and triiodothyronine receptors in mouse brain

It is known that alcohol induces disorders in the metabolism of retinoids and particularly in the biosynthetic pathways of retinoic acid (RA). Since RA has, along with other hormones and particularly triiodothyronine (T3), a physiological role in the adult brain, the effect of chronic exposure to alcohol on RA and T3 status was investigated. The amounts of RA receptor (RAR) and T3 receptor (TR) mRNAs were quantified and the activity of the 'tissue' transglutaminase (tTG; an RA-dependent enzyme) was assayed in the brain of mice following chronic ethanol consumption (CEC; 12% v/v for 6-10 months). Compared to controls, ethanol-treated mice exhibited increased amounts of RAR and TR mRNAs together with an increase in tTG activity. It is hypothesized that the enhanced cellular action of RA and T3 could play a role in the previously described brain damages induced by CEC.

Synapse-to-neuron ratio in the lateral geniculate nucleus of rats exposed chronically to ethanol

Effects of chronic ethanol exposure on synapse-to-neuron ratio in the rat lateral geniculate nucleus were investigated. Male Sprague-Dawley rats were exposed to ethanol, using the Lieber-DeCarli liquid diets, for 4 months starting at the age of 5 weeks. Brains were perfusion-fixed, and the region containing the dorsal lateral geniculate nucleus was cut into slabs (500 microns thick) that were epoxy resin-embedded. From each rat, three slabs containing the structure were serially sectioned for electron microscopy. Using the double disector method, the study shows an unaltered synapse-to-neuron ratio in ethanol-treated rats when compared with controls. The findings are in agreement with previous studies on the visual system using the same exposure model. In contrast, a previous study has shown that the synapse-to-neuron ratio in locus ceruleus of ethanol-treated rats is reduced by 50%. Other studies have shown that, whereas the glutamatergic NMDA receptor is very sensitive to ethanol, the kainate/AMPA type of receptor is very much less so. Thus, the difference in ethanol-induced synapse elimination between the two regions may reflect this different sensitivity of the glutamatergic receptors, which are of the kainate/AMPA type in the lateral geniculate nucleus and of the NMDA type in the locus ceruleus.

Structural reorganization in the supraoptic nucleus of withdrawn rats following long-term alcohol consumption

We have recently shown in the supraoptic nucleus (SON) of the rat that prolonged ethanol consumption induces cell degeneration and enlargement of the surviving neurons and of their subcellular organelles. We analyzed the SON of withdrawn rats to evaluate whether it displays any evidence of morphological reorganization following abstinence from ethanol, inasmuch as in this condition the ethanol-induced changes in the plasma levels of neurohormones and plasma osmolality are no longer detectable. A group of 18-month-old withdrawn rats was compared with age-matched, pair-fed control and ethanol-treated rats. To differentiate between the effects of withdrawal and the effects of rehydration, a group of 18-month-old rehydrated rats was also included in this study and compared with age-matched, pair-fed control and dehydrated rats. We estimated the volume of SON, and the total number and mean volume of its neurons. The cross-sectional areas of the vasopressinergic and oxytocinergic populations were also evaluated. At the ultrastructural level, we determined the volumes and surface areas of the rough endoplasmic reticulum and Golgi apparatus, and the volumes of neurosecretory granules and nucleoli. In withdrawn animals, the total number of SON neurons was smaller than in controls, although the neuronal volume was greater. The number of SON neurons did not differ between withdrawn and ethanol-treated rats, despite the reduced volume of SON in the former animals. The decrease of SON volume correlated with and was caused by a reduction in the volume of SON neurons and in the size of the organelles involved in neuro-hormone synthesis.(ABSTRACT TRUNCATED AT 250 WORDS)

Anterior hippocampal volume deficits in nonamnesic, aging chronic alcoholics

Magnetic resonance imaging was used to quantify the volume of the hippocampus in 47 men with chronic alcoholism and 72 healthy male control subjects. The subjects ranged in age from 21 to 70 years, thus permitting a test of whether older alcoholics suffer greater brain tissue volume reduction than do younger ones. Comparison brain regions included temporal lobe gray matter, white matter, and cerebrospinal fluid, as well as measures of the lateral ventricles, third ventricle, and temporal horns. The results of this cross-sectional study showed that the anterior, but not the posterior, portions of the hippocampus in both hemispheres were significantly smaller in the alcoholic than the healthy control group. Furthermore, the bilateral anterior hippocampal volume loss was greater in older than younger alcoholics. Despite the hippocampal volume deficit, these alcoholics did not demonstrate an explicit memory impairment; furthermore, memory test scores did not correlate significantly with hippocampal volumes. In the alcoholics, the age-related volume loss, which was over and above that expected in normal aging, was also evident in the temporal cortex and white matter. Likewise, alcoholic ventricular enlargement was age-related. Analysis of covariance revealed that the anterior hippocampal deficit persisted after accounting for the temporal lobe gray matter volume deficit. Multiple regression analysis revealed that the age-related brain volume abnormalities observed in the alcoholics could not be attributed to duration of alcoholism or total lifetime consumption of alcohol.

Long-term effects of intermittent versus continuous ethanol exposure on hippocampal synapses of the rat

The hippocampus is known to be very sensitive to a large spectrum of different neurotoxins including ethanol. Ethanol administered continuously or intermittently may affect the hippocampus in different ways. Intermittent administration of ethanol has many features in common with the low level electrical stimulation protocols which lead to the functional changes associated with the phenomenon of kindling. In this study, the differential effects of intermittent intraperitoneal ethanol injections (3 g/kg twice daily) and continuously administered ethanol in drinking water (20%) on hippocampal synapses in the rat were studied using ethanolic phosphotungstic acid staining and electron microscopy. After 1 month of intermittent exposure a significant reduction (18%) of synapses was seen in the stratum lucidum of the CA3 region. Continuously treated animals showed no significant change over this time despite a higher total ethanol intake. In the dentate gyrus, a compensatory increase in supragranular synaptic number was seen only in continuously treated animals. These findings demonstrate the sensitivity of synapses of the hippocampus to the presence of ethanol and the larger effects of peaking ethanol concentrations compared to more constant levels. These results emphasize the need to consider the differential effects of various types of ethanol consumption also on the human brain.

Effects of chronic alcohol consumption and of dehydration on the supraoptic nucleus of adult male and female rats

Ethanol ingestion affects the hypothalamo-neurohypophysial system resulting in increased diuresis, dehydration and hyperosmolality. We studied the supraoptic nucleus, of the hypothalamus, in ethanol-treated rats, to determine if ethanol alone and/or the associated disturbances of water metabolism lead to structural alterations in a nucleus known to play a central role in fluid homeostasis. Groups of male and female rats were ethanol-treated until 12 and 18 months of age and compared with age-matched pair-fed controls. Twelve and 18-month-old control groups and 12-month-old water control groups (rats submitted to chronic dehydration) were also included in this study in an attempt to differentiate between the effects of undernutrition and dehydration/hyperosmolality, and the specific neurotoxic effects of ethanol. We estimated the volume of the supraoptic nucleus and the numerical density of its neurons and calculated the total number of supraoptic neurons. The volume of both supraoptic neurons and neuropil were also estimated. In immunostained material the ratio of vasopressin to oxytocin neurons and the cross-sectional areas of the two neuronal types were evaluated. There was marked neuronal loss in alcohol-treated rats, but the volume of the supraoptic nucleus was increased. The increase in the volume of the supraoptic nucleus correlated with and was due to increases in the volume was particularly marked for vasopressin neurons. No significant differences were found between controls and pair-fed controls in any of the parameters investigated. In water control rats, the volume of the supraoptic nucleus and of the supraoptic neurons and neuropil was also greater than in pair-fed controls. However, the variations found were not as marked as in ethanol-treated rats and there was no cell loss. These findings reveal, for the first time, that chronic ethanol consumption affects the morphology of supraoptic neurons and neuropil and, consequently, the structure of the entire supraoptic nucleus. Moreover, this study supports the view that ethanol has direct neurotoxic effects on supraoptic neurons because the alterations that occur are not mimicked in animals in which water metabolism alone is disturbed.

Alterations and recovery of rat brain gangliosides and glycosidases following long-term exposure to alcohol and rehabilitation during development

The present study examines effects of continuous exposure to alcohol during gestation, lactation and postweaning periods and rehabilitation on gangliosides and their catabolizing enzymes in whole brain (WB), cerebrum (C), cerebellum (CB) and brain stem (BS) of 63-day-old rats. Continuous exposure to alcohol was found to cause significant deficits in the body and brain weights. On the other hand, the concentration of total ganglioside in whole brain, cerebrum, cerebellum and brain stem showed an increase following exposure to alcohol. In agreement with the increased ganglioside concentration the activities of sialidase, beta-galactosidase, beta-glucosidase and beta-hexosaminidase, which are likely to be involved in the catabolism of gangliosides, showed reductions due to alcohol. Alcohol was also found to alter the proportions of individual gangliosides and the changes were found to be region-specific. However; the alcohol-induced alterations were reversed, at least to some extent, upon abstinence from alcohol. Body weights of control (CT), alcoholic (AC) and rehabilitated (AR) rats were 164 +/- 2, 107 +/- 7 and 139 +/- 3 (mean +/- S.E.M.), respectively. Decrease in tissue weight was significant in whole brain, cerebrum and brain stem but not in cerebellum. In AR rats significant deficits in tissue weights persisted in cerebrum and almost a complete recovery was observed in brain stem. On the other hand, the increase in the concentration of gangliosides in WB, C, CB and BS of AC rats amounted to 23, 19, 19 and 53% of controls, respectively. The corresponding values for the AR rats were 12, 14, 3 and 5%, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Decreased synapse-to-neuron ratio in rat locus ceruleus following chronic ethanol feeding

Effects of chronic ethanol exposure on the synapse-to-neuron ratio of rat locus ceruleus were investigated. Male Sprague-Dawley rats were given an ethanol-containing liquid diet for 4 months starting at an age of 5 weeks. Littermates, given isocaloric amounts of an ethanol-free diet, served as control. The animals were perfusion fixed using a mixture of glutaraldehyde and paraformaldehyde. Synapse-to-neuron ratio was estimated by the double disector method and calculated from (Ns/A) x (Nsec -1) / (Nn/A) where Ns/A is the number of synapses per unit area estimated in a disector with a height of on section and Nsec -1 is height of the disector, i.e., the number of sections, used for estimating the number of neurons per area (Nn/A). The mean estimated synapse-to-neuron ratio was 2046 +/- 544 (SD) in ethanol-fed rats and 4291 +/- 1171 (SD) in control rats. The difference is statistically significant (p < 0.05). The finding may be of relevance for understanding the development of abuse, tolerance, drug dependence, and abstinence reactions.

Effect of chronic ethanol on the septohippocampal system: a role for neurotrophic factors?

The mechanisms by which chronic ethanol exposure produces neuronal damage have not been established. Potentially ethanol may reduce normal neurotrophic influences necessary for neuronal survival, growth, and function. We hypothesized that chronic ethanol exposure might produce a decrease in the synthesis, availability, upregulation, delivery, and/or the biological activity of normally occurring neurotrophic factors, or may alter the capacity of target neurons to respond to these factors. The available evidence leading to this hypothesis and supporting data from our laboratory are discussed.

Structural changes in the hippocampal formation after long-term alcohol consumption and withdrawal in the rat

The effects of long-term alcohol consumption and withdrawal upon the structure of the rat hippocampal formation were studied by applying morphometric methods to material processed for light and electron microscopy. The somatostatinergic neurons of the hilus were also studied. Groups of 6 rats were treated as follows: (a) given alcohol for 6, 12 and 18 months; (b) paired controls; and (c) rats switched to a normal diet in the 6 months after 6 and 12 months of alcohol intake. A progressive loss of hippocampal neurons after chronic alcohol consumption was found. The loss was aggravated during withdrawal from alcohol, with the exception of the hilar cells. The dendrites of granule cells from the alcohol-treated rats displayed signs of regrowing, but they did not do so in rats withdrawn from alcohol. The synapses between mossy fibre terminals and CA3 dendrites appear to be rather resistant to alcohol insult, and evidence of morphological plasticity was found in withdrawn rats. If an homology can be established between humans and rodents then the changes observed in alcohol-fed rats can be regarded as underpinning some of the functional and behavioural alterations depicted under these circumstances. The peculiar changes found in some nerve cell populations after withdrawal of alcohol could be related to the deficient or incomplete functional recovery often seen after abstinence from alcohol.

Decreased axonal calibres without axonal loss in optic nerve following chronic alcohol feeding in adult rats: a morphometric study

The effects of chronic ethanol exposure on number and calibres of optic nerve axons (and number of retinal ganglion cells) were investigated in a rat model. Male Sprague-Dawley rats were fed a liquid, ethanol-containing diet for 5, 10 and 17 weeks with littermates given isocaloric amounts of ethanol-free diet serving as controls. After fixation by perfusion, the optic nerves were imbedded in epoxy resin and sectioned for electron microscopy. Systematic random sampling was made from a cross-shaped area over the nerve. Axons within a counting frame were counted and morphometrically categorized with regard to mean diameter and the total number of axons estimated from number per area and the cross-sectional area of the nerve, which was measured using a digitizer table. According to non-parametric statistical analysis, ethanol exposure resulted in a significant reduction in mean cross-sectional area of the optic nerve and in mean axonal calibre but not in total axonal number in the ethanol-treated rats but there was no significant effect of duration of the exposure. The mean cross-sectional area of the nerve was reduced by 9%, 10% and 18% after 5, 10 and 17 weeks of exposure, respectively. The reduction in cross-sectional area appeared to be related to a proportional reduction in axonal and myelin area fractions. The findings indicate that chronic ethanol exposure results in decreased axonal calibres without axonal loss. This also implies that there is no reduction in the number of retinal ganglion cells.

The effect of chronic ethanol intake on brain NGF level and on NGF-target tissues of adult mice

The effect of ethanol consumption on the forebrain and hypothalamus of adult mice was investigated. A consistent decrease of biological activity and of nerve growth factor (NGF) immunoreactivity was observed in the hippocampus and hypothalamus of alcohol-treated mice. Biochemical studies also indicate that chronic ethanol intake causes a reduction in the level of choline-acetyltransferase in the septum, hippocampus and striatum, but not in the cortex and other brain regions. This study provides evidence that long-term ethanol intake causes impairment of brain NGF level and of the cholinergic enzyme, regulated by NGF, suggesting that NGF synthesis and/or biological activity is affected in alcohol-related brain neuropathology.

The effect of long-term alcohol intake on brain NGF-target cells of aged rats

It was reported that chronic exposure to ethanol causes a loss of hippocampal pyramidal cells and of brain cholinergic neurons in both laboratory animals and humans. In the present study, it was hypothesized that nerve growth factor (NGF), a trophic agent for the survival and maintenance of basal forebrain cholinergic neurons (FCN), might be affected by the neurodegenerative events which occur during ethanol consumption. To test this hypothesis, we used aged rats (14 months) exposed for 16 weeks to 40 g/kg per day of undiluted wine. Our experiments showed that chronic alcohol consumption causes a reduction of NGF in the hippocampus (HI) and of choline acetyltransferase (ChAT) activity in both the septum and the HI and a reduction in the distribution of NGF-receptors (NGF-R) in the septum and nucleus of Meynert. Intracerebral injection of NGF in alcohol-exposed rats results in a return to normal levels of ChAT enzymatic activity and NGF-R expression. These experiments indicate that the damaging effect of alcohol on the FCN is also associated with impairment of central NGF-target structures.

Effects of GM1 ganglioside upon neuronal degeneration during withdrawal from alcohol

In previous studies we demonstrated that chronic alcohol consumption induced hippocampal cell and synapse loss in offset with an increase in the length of granule cell dendrites. In addition we observed that withdrawal after long periods of alcohol intake worsened the degenerative processes and that dendritic alterations were no longer apparent. In an attempt to reverse these structural changes we tested the action of GM1 ganglioside during the withdrawal period as there is evidence that GM1 may enhance neuronal recovery after different kinds of brain lesions. Cell and synaptic quantifications were performed and the branching pattern of the granule cell dendritic arborizations was analysed. The number of dentate granule and CA3 pyramidal cells from GM1-treated animals was found not to be significantly different from that of the alcohol-treated and withdrawal groups. No quantitative changes were found in the number of mossy fiber-CA3 pyramidal cell synapses when the aforementioned groups were compared. Whether the lack of effectiveness of GM1 can be related to the model employed or not is thoroughly discussed.